Success rates in pediatric WPW ablation are improved with 3-dimensional mapping systems compared with fluoroscopy alone: a multicenter study.

INTRODUCTION: Three-dimensional mapping (3-D) systems are frequently used for ablation of supraventricular tachycardia. Prior studies have demonstrated radiation dosage reduction with 3-D, but there are no data on whether 3-D improves the efficacy of ablation of Wolff-Parkinson-White syndrome (WPW). We sought to determine if 3-D improves the success rate for ablation of WPW in children. METHODS: Multicenter retrospective study including patients ≤21 years of age with WPW undergoing ablation from 2008 to 2012. Success rates using the 2 techniques (3-D vs. fluoroscopy alone [FLUORO]) were compared. RESULTS: Six hundred and fifty-one cases were included (58% male, mean age 13 ± 4 years, 366 [56%] 3-D). Baseline characteristics including gender, weight, accessory pathway (AP) location, number of APs, and repeat ablation attempts were similar between the 2 groups (3-D and FLUORO) The 3-D group was slightly younger (12.7 ± 4.0 vs. 13.3 ± 4.0 years; P = 0.04) and less likely to undergo ablation utilizing cryoenergy (38 [10%] vs. 56 [20%]; P < 0.01). The 3-D group had a higher acute success rate of ablation (355 [97%] vs. 260 [91%]; P < 0.01). No differences were seen in recurrence (16 [5%] vs. 26 [9%]; P = 0.09) or complication rates (1 [0.3%] vs. 1 [0.4%]; P = 0.86) between the groups. On multivariable analysis, 3-D was shown to significantly improve success at ablation with an odds ratio of 3.1 (95% CI 1.44-6.72; P < 0.01). CONCLUSIONS: Use of 3-D significantly improved success rates for ablation of WPW in children. The increase in acute success associated with 3-D suggests it is an important adjunct for catheter ablation of WPW in children.

Three-Catheter Technique for Ablation of Left-Sided Accessory Pathways in Wolff-Parkinson-White is Less Expensive and Equally Successful When Compared to a Five-Catheter Technique.

PURPOSE: To compare the efficacy, safety, and cost-effectiveness of a three-catheter approach with a conventional five-catheter approach for the mapping and ablation of supraventricular tachycardia in pediatric patients with Wolff-Parkinson-White Syndrome (WPW) and concealed accessory pathways (APs). METHODS: A retrospective review from 2008 to 2012 of patients less than 21 years with WPW who underwent a three-catheter radiofrequency (RF) ablation of a left-sided AP (ablation, right ventricular [RV] apical, and coronary sinus [CS] decapolar catheters) was performed. The three-catheter group was compared to a control group who underwent a standard five-catheter (ablation, RV apical, CS decapolar, His catheter, and right atrial catheter) ablation for the treatment of left-sided WPW or concealed AP. Demographics, ablation outcomes, and costs were compared between groups. RESULTS: Twenty-eight patients met inclusion criteria with 28 control patients. The groups did not differ in gender, age, weight, or body surface area. Locations of the AP on the mitral annulus were similar between the groups. All patients were ablated via transseptal approach. Note that 28 of 28 in the three-catheter group (100%) and 27 of 28 (96%) controls were acutely successfully ablated (P = 0.31). No complications were encountered. There was no difference in procedural time, time to loss of AP conduction, or number of RF applications. Use of the three-catheter technique resulted in a total savings of $2,465/case, which includes the $680 savings from using fewer catheters as well as the savings from a shortened procedure time. CONCLUSIONS: Ablation in patients with WPW and a left-sided AP can be performed using three catheters with similar efficacy and safety while offering significant cost savings compared to a conventional five-catheter approach.

The prevalence of arrhythmias, predictors for arrhythmias, and safety of exercise stress testing in children.

Exercise testing is commonly performed in children for evaluation of cardiac disease. Few data exist, however, on the prevalence, types of arrhythmias, predictors for arrhythmias, and safety of exercise testing in children. A retrospective review of all patients ≤21 years undergoing exercise testing at our center from 2008 to 2012 was performed. Patients with clinically relevant arrhythmias were compared to those not experiencing a significant arrhythmia. 1,037 tests were performed in 916 patients. The mean age was 14 ± 4 years, 537 (55 %) were male, 281 (27 %) had congenital heart disease, 178 (17 %) had a history of a prior arrhythmia, and 17 (2 %) had a pacemaker or ICD. 291 (28 %) patients had a rhythm disturbance during the procedure. Clinically important arrhythmias were noted in 34 (3 %) patients and included: 19 (1.8 %) increasing ectopy with exercise, 5 (0.5 %) VT, 5 (0.5 %) second degree AV block, 3 (0.3 %) SVT, and 2 (0.2 %) AFIB. On multivariate logistic regression, variables associated with the development of clinically relevant arrhythmias included severe left ventricular (LV) dysfunction on echo (OR 1.99, CI 1.20-3.30) and prior history of a documented arrhythmia (OR 2.94, CI 1.25-6.88). There were no adverse events related to testing with no patient requiring cardioversion, defibrillation, or acute anti-arrhythmic therapy. A total of 28 % of children developed a rhythm disturbance during exercise testing and 3 % were clinically important. Severe LV dysfunction and a history of documented arrhythmia were associated with the development of a clinically important arrhythmia.

Lone atrial fibrillation in the young - perhaps not so "lone"?

OBJECTIVE: To determine if pediatric patients with a history of lone atrial fibrillation (AF) have other forms of supraventricular tachycardia (SVT) that may potentially trigger AF. STUDY DESIGN: A multicenter review of patients with lone AF who underwent electrophysiology (EP) study from 2006-2011 was performed. INCLUSION CRITERIA: age ≤21 years, normal ventricular function, structurally normal heart, history of AF, and EP study and/or ablation performed. EXCLUSION CRITERIA: congenital heart disease or cardiomyopathy. Patient demographics, findings at EP study and follow-up data were recorded. RESULTS: Eighteen patients met inclusion criteria. The mean age was 17.9 ± 2.2 years, weight was 82 ± 21 kg, body mass index was 27 ± 6, and 15 (83%) were males. Eleven (61%) were overweight or obese. Seven (39%) had inducible SVT during EP study: 5 atrioventricular nodal re-entry tachycardia (71%) and 2 concealed accessory pathways with inducible atrioventricular re-entry tachycardia (29%). All 7 patients with inducible SVT underwent radiofrequency ablation. There were no complications during EP study and/or ablation for all 18 patients. The mean follow-up was 1.7 ± 1.5 years and there were no recurrences in the 7 patients who underwent ablation. There were 2 recurrences of AF in patients with no other form of SVT during EP study. CONCLUSIONS: Inducible SVT was found in 39% of pediatric patients undergoing EP study for lone AF. EP study should be considered for pediatric patients presenting with lone AF.

Reducing patient radiation dosage during pediatric SVT ablations using an "ALARA" radiation reduction protocol in the modern fluoroscopic era.

BACKGROUND: Ablation for supraventricular tachycardia (SVT) relies upon fluoroscopy (fluoro), which exposes the patient and staff to ionizing radiation. The objective of this work was to present a new "ALARA--As Low As Reasonably Achievable" protocol with alterations to fluoroscopic x-ray parameters to reduce dose without an electroanatomical (EAM) approach. METHODS: All patients <21 years of age undergoing ablation of SVT at our institution from June 2011 to April 2012 were included. EAM was not utilized in any case. An ALARA protocol of low frame rates (2 or 3 fps), low fluoro dose/frame (10-18 nGy/frame), and other techniques aimed at reducing use of fluoroscopy were employed. Demographics, procedural, and radiation data were analyzed. RESULTS: Forty-two patients underwent ablation and were studied. Median age was 14.1 years (range 4.8-21.1 years), weight was 51 kg (range 18.2-75 kg), and body surface area was 1.51 m(2) (range 0.72- 1.94 m(2)). Seventeen (41%) had Wolff-Parkinson-White syndrome, 14 (33%) atrioventricular nodal reentrant tachycardia, and 11 (26%) concealed pathways. Median procedural time was 114 minutes (57-246 minutes). Median dose area product (DAP) for posterioanterior and lateral fluoroscopy was 343.2 uGym(2) (range 38.2-3,172 uGym(2)); the median air Kerma product (K) was 45.4 mGy (range 6.7-567.5 mGy). DAP and K are lower than prior data from EAM and fluoroscopy techniques. The acute success rate was 95%; no procedural complications. CONCLUSIONS: An ALARA protocol for ablation of SVT reduced radiation to below levels previously reported for combined EAM/fluoro approaches. Success rates were excellent with no complications and without the costs of EAM.

Clinical and electrophysiologic characteristics of antidromic tachycardia in children with Wolff-Parkinson-White syndrome.

BACKGROUND: Antidromic reciprocating tachycardia (ART) is a rare form of wide complex tachycardia in children with Wolff-Parkinson-White syndrome (WPW). The incidence and electrophysiologic characteristics of ART in children with WPW have not been well described. METHODS: A multicenter retrospective analysis of all patients with WPW undergoing electrophysiology (EP) study from 1990 to 2009 was performed. Patients with clinical or inducible ART were included. RESULTS: A total of 1,147 patients with WPW underwent EP study and 30 patients had ART (2.6%) and were the subject of this analysis. The mean age was 16±3 years, weight was 65±16 kg, and tachycardia cycle length was 305±55 ms. There were two patients (7%) with congenital heart disease (both with Ebstein's anomaly). Four patients (13%) had more than one accessory pathway (AP). The location of the AP was left sided in 53% of patients and right sided in 47%, with septal location and left lateral pathways most commonly involved. AP conduction was found to be high risk in 17 patients (57%). Ablation was not attempted in two patients (7%) due to proximity to the HIS and risk of heart block. Ablation was acutely successful in 93% of the patients in whom it was attempted. CONCLUSIONS: ART is a rare finding in children undergoing EP study. Over half of the patients with ART were found to be high risk and multiple AP were uncommon. Unlike the adult population, ART occurred commonly with septal APs.

Loss of ventricular preexcitation during noninvasive testing does not exclude high-risk accessory pathways: A multicenter study of WPW in children.

BACKGROUND: Abrupt loss of ventricular preexcitation on noninvasive evaluation, or nonpersistent preexcitation, in Wolff-Parkinson-White syndrome (WPW) is thought to indicate a low risk of life-threatening events. OBJECTIVE: The purpose of this study was to compare accessory pathway (AP) characteristics and occurrences of sudden cardiac arrest (SCA) and rapidly conducted preexcited atrial fibrillation (RC-AF) in patients with nonpersistent and persistent preexcitation. METHODS: Patients 21 years or younger with WPW and invasive electrophysiology study (EPS) data, SCA, or RC-AF were identified from multicenter databases. Nonpersistent preexcitation was defined as absence/sudden loss of preexcitation on electrocardiogram, Holter monitoring, or exercise stress test. RC-AF was defined as clinical preexcited atrial fibrillation with shortest preexcited R-R interval (SPERRI) ≤ 250 ms. AP effective refractory period (APERP), SPERRI at EPS , and shortest preexcited paced cycle length (SPPCL) were collected. High-risk APs were defined as APERP, SPERRI, or SPPCL ≤ 250 ms. RESULTS: Of 1589 patients, 244 (15%) had nonpersistent preexcitation and 1345 (85%) had persistent preexcitation. There were no differences in sex (58% vs 60% male; P=.49) or age (13.3±3.6 years vs 13.1±3.9 years; P=.43) between groups. Although APERP (344±76 ms vs 312±61 ms; P<.001) and SPPCL (394±123 ms vs 317±82 ms; P<.001) were longer in nonpersistent vs persistent preexcitation, there was no difference in SPERRI at EPS (331±71 ms vs 316±73 ms; P=.15). Nonpersistent preexcitation was associated with fewer high-risk APs (13% vs 23%; P<.001) than persistent preexcitation. Of 61 patients with SCA or RC-AF, 6 (10%) had nonpersistent preexcitation (3 SCA, 3 RC-AF). CONCLUSION: Nonpersistent preexcitation was associated with fewer high-risk APs, though it did not exclude the risk of SCA or RC-AF in children with WPW.

Validation of a novel automated signal analysis tool for ablation of Wolff-Parkinson-White Syndrome.

BACKGROUND: In previous pilot work we demonstrated that a novel automated signal analysis tool could accurately identify successful ablation sites during Wolff-Parkinson-White (WPW) ablation at a single center. OBJECTIVE: We sought to validate and refine this signal analysis tool in a larger multi-center cohort of children with WPW. METHODS: A retrospective review was performed of signal data from children with WPW who underwent ablation at two pediatric arrhythmia centers from 2008-2015. All patients with WPW ≤ 21 years who underwent invasive electrophysiology study and ablation with ablation signals available for review were included. Signals were excluded if temperature or power delivery was inadequate or lesion time was < 5 seconds. Ablation lesions were reviewed for each patient. Signals were classified as successful if there was loss of antegrade and retrograde accessory pathway (AP) conduction or unsuccessful if ablation did not eliminate AP conduction. Custom signal analysis software analyzed intracardiac electrograms for amplitudes, high and low frequency components, integrated area, and signal timing components to create a signal score. We validated the previously published signal score threshold 3.1 in this larger, more diverse cohort and explored additional scoring options. Logistic regression with lasso regularization using Youden's index criterion and a cost-benefit criterion to identify thresholds was considered as a refinement to this score. RESULTS: 347 signals (141 successful, 206 unsuccessful) in 144 pts were analyzed [mean age 13.2 ± 3.9 years, 96 (67%) male, 66 (45%) left sided APs]. The software correctly identified the signals as successful or unsuccessful in 276/347 (80%) at a threshold of 3.1. The performance of other thresholds did not significantly improve the predictive ability. A signal score threshold of 3.1 provided the following diagnostic accuracy for distinguishing a successful from unsuccessful signal: sensitivity 83%, specificity 77%, PPV 71%, NPV 87%. CONCLUSIONS: An automated signal analysis software tool reliably distinguished successful versus unsuccessful ablation electrograms in children with WPW when validated in a large, diverse cohort. Refining the tools using an alternative threshold and statistical method did not improve the original signal score at a threshold of 3.1. This software was effective across two centers and multiple operators and may be an effective tool for ablation of WPW.

Impact of intermittent hypoxia on long-term facilitation of minute ventilation and heart rate variability in men and women: do sex differences exist?

Following exposure to intermittent hypoxia, respiratory motor activity and sympathetic nervous system activity may persist above baseline levels for over an hour. The present investigation was designed to determine whether sustained increases in minute ventilation and sympathovagal (S/V) balance, in addition to sustained depression of parasympathetic nervous system activity (PNSA), were greater in men compared with women following exposure to intermittent hypoxia. Fifteen healthy men and women matched for age, race, and body mass index were exposed to eight 4-min episodes of hypoxia during sustained hypercapnia followed by a 15-min end-recovery period. The magnitude of the increase in minute ventilation during the end-recovery period, compared with baseline, was similar in men and women (men, 1.52 +/- 0.03; women, 1.57 +/- 0.02 fraction of baseline; P < 0.0001). In contrast, depression of PNSA and increases in S/V balance were evident during the end-recovery period, compared with baseline, in men (PNSA, 0.66 +/- 0.06 fraction of baseline, P < 0.0001; S/V balance, 2.8 +/- 0.7 fraction of baseline, P < 0.03) but not in women (PNSA, 1.27 +/- 0.19 fraction of baseline, P = 0.3; S/V balance, 1.8 +/- 0.6 fraction of baseline, P = 0.2). We conclude that a sustained increase in minute ventilation, which is indicative of long-term facilitation, is evident in both men and women following exposure to intermittent hypoxia and that this response is independent of sex. In contrast, sustained alterations in autonomic nervous system activity were evident in men but not in women.

Initial experience with the 3.3 Fr Mongoose® pigtail catheter for aortic angiography during patent ductus arteriosus closure in small patients.

BACKGROUND: Smaller femoral arterial sheaths may be associated with fewer vascular complications. The 3.3 Fr Mongoose® Pediavascular pigtail catheter is a catheter that allows higher flow rates, potentially resulting in improved angiographic quality. We reviewed our experience with this small catheter during patent ductus arteriosus (PDA) closure. MATERIALS AND METHODS: Review of patients ≤20 kg in whom the Mongoose® catheter was used during PDA closure from 12/13 to 4/15. Angiographic efficacy and procedural details were compared to ten 4 Fr catheter cases. Comparisons were performed using Mann-Whitney U-test; P < 0.05 was statistically significant. RESULTS: Twelve (9 female) patients were catheterized with a 3.3 Fr Mongoose®. Median weight 10.5 kg (range 6.4-18.2), height 81 cm (range 37-111), and body surface area (BSA) 0.47 m2 (range 0.33-0.75) were similar to ten patients (3 females) in the 4 Fr control group (P = NS); median weight 9.9 kg (range 6-16.8), height 80 cm (range 64-102), and BSA 0.46 m2 (range 0.31-0.74). Angiographic quality was subjectively adequate with both with no difference in the median pixel density between the two techniques (3.3 Fr: 76.7 [range 33.5-90] and 4 Fr: [70; 38-102]; P = NS). Contrast used was similar between the groups (3.3 Fr: median 4.2 ml/kg and 4 Fr: 4.9 ml/kg; P = NS). Median radiation dose was similar in the two groups (3.3 Fr: 28.1 mGy [range 17.2-38] and 4 Fr: 38 mGy [range 20.4-58.5]; P = NS). All ducts were closed at latest follow-up (P = NS). No complications were encountered. CONCLUSIONS: The 3.3 Fr Mongoose® allowed similar angiography to the 4 Fr pigtail catheter, allowing safe and effective transcatheter PDA closure in small children.

Increased sympathetic and decreased parasympathetic cardiovascular modulation in normal humans with acute sleep deprivation.

Cardiovascular autonomic modulation during 36 h of total sleep deprivation (SD) was assessed in 18 normal subjects (16 men, 2 women, 26.0 +/- 4.6 yr old). ECG and continuous blood pressure (BP) from radial artery tonometry were obtained at 2100 on the first study night (baseline) and every subsequent 12 h of SD. Each measurement period included resting supine, seated, and seated performing computerized tasks and measured vigilance and executive function. Subjects were not supine in the periods between measurements. Spectral analysis of heart rate variability (HRV) and BP variability (BPV) was computed for cardiac parasympathetic modulation [high-frequency power (HF)], sympathetic modulation [low-frequency power (LF)], sympathovagal balance (LF/HF power of R-R variability), and BPV sympathetic modulation (at LF). All spectral data were expressed in normalized units [(total power of the components/total power-very LF) x 100]. Spontaneous baroreflex sensitivity (BRS), based on systolic BP and pulse interval powers, was also measured. Supine and sitting, BPV LF was significantly increased from baseline at 12, 24, and 36 h of SD. Sitting, HRV LF was increased at 12 and 24 h of SD, HRV HF was decreased at 12 h SD, and HRV LF/HF power of R-R variability was increased at 12 h of SD. BRS was decreased at 24 h of SD supine and seated. During the simple reaction time task (vigilance testing), the significantly increased sympathetic and decreased parasympathetic cardiac modulation and BRS extended through 36 h of SD. In summary, acute SD was associated with increased sympathetic and decreased parasympathetic cardiovascular modulation and decreased BRS, most consistently in the seated position and during simple reaction-time testing.

Heart rate variability in non-apneic snorers and controls before and after continuous positive airway pressure.

BACKGROUND: We hypothesized that sympathetic nervous system activity (SNSA) is increased and parasympathetic nervous system activity (PNSA) is decreased during non-rapid eye movement (NREM) sleep in non-apneic, otherwise healthy, snoring individuals compared to control. Moreover, we hypothesized that these alterations in snoring individuals would be more evident during non-snoring than snoring when compared to control. METHODS: To test these hypotheses, heart rate variability was used to measure PNSA and SNSA in 11 normotensive non-apneic snorers and 12 control subjects before and 7-days after adapting to nasal continuous positive airway pressure (nCPAP). RESULTS: Our results showed that SNSA was increased and PNSA was decreased in non-apneic snorers during NREM compared to control. However, these changes were only evident during the study in which snoring was eliminated with nCPAP. Conversely, during periods of snoring SNSA and PNSA were similar to measures obtained from the control group. Additionally, within the control group, SNSA and PNSA did not vary before and after nCPAP application. CONCLUSION: Our findings suggest that long-lasting alterations in autonomic function may exist in snoring subjects that are otherwise healthy. Moreover, we speculate that because of competing inputs (i.e. inhibitory versus excitatory inputs) to the autonomic nervous system during snoring, the full impact of snoring on autonomic function is most evident during non-snoring periods.

Improving ECG Services at a Children's Hospital: Implementation of a Digital ECG System.

Background. The use of digital ECG software and services is becoming common. We hypothesized that the introduction of a completely digital ECG system would increase the volume of ECGs interpreted at our children's hospital. Methods. As part of a hospital wide quality improvement initiative, a digital ECG service (MUSE, GE) was implemented at the Children's Hospital at Montefiore in June 2012. The total volume of ECGs performed in the first 6 months of the digital ECG era was compared to 18 months of the predigital era. Predigital and postdigital data were compared via t-tests. Results. The mean ECGs interpreted per month were 53 ± 16 in the predigital era and 216 ± 37 in the postdigital era (p < 0.001), a fourfold increase in ECG volume after introduction of the digital system. There was no significant change in inpatient or outpatient service volume during that time. The mean billing time decreased from 21 ± 27 days in the postdigital era to 12 ± 5 days in the postdigital era (p < 0.001). Conclusion. Implementation of a digital ECG system increased the volume of ECGs officially interpreted and reported.

Baroreflex sensitivity in nonapneic snorers and control subjects before and after nasal continuous positive airway pressure.

HYPOTHESIS: We hypothesized that baroreflex sensitivity is decreased during wakefulness and non-rapid eye movement sleep in normotensive, nonapneic snorers who are otherwise healthy. Moreover, we hypothesized that nocturnal alterations in baroreflex sensitivity are abolished during the application of nasal continuous positive airway pressure (nCPAP). DESIGN: The sequencing technique was used to measure baroreflex sensitivity in 16 normotensive nonapneic snorers and 16 control subjects matched for age, height, weight, gender, and race. Subsequently, baroreflex sensitivity was measured in 12 of 16 snorers and 14 of 16 control subjects during the application of nCPAP. RESULTS: Mean (+/- SE) baroreflex sensitivity was reduced during sleep in the nonapneic snoring group (wakefulness, 20.99 +/- 1.46 ms/mm Hg; sleep, 15.85 +/- 1.49 ms/mm Hg), but not in the control group (wakefulness, 21.82 +/- 2.48 ms/mm Hg; sleep, 23.54 +/- 2.18 ms/mm Hg). This reduction was abolished by the application of nCPAP in the snoring group (before nCPAP therapy, 16.30 +/- 2.17 ms/mm Hg; during nCPAP therapy, 20.63 +/- 2.40 ms/mm Hg). The application of nCPAP did not alter baroreflex sensitivity in the control group (before nCPAP therapy, 23.54 +/- 2.18 ms/mm Hg; during nCPAP therapy, 22.56 +/- 1.73 ms/mm Hg). BP was not significantly different between the snoring and control groups either before or during nCPAP application. CONCLUSIONS: Our findings suggest that nocturnal alterations in baroreflex sensitivity may exist in nonapneic snoring subjects prior to alterations in other cardiovascular variables.

Novel method of signal analysis for ablation of Wolff-Parkinson-White syndrome.

BACKGROUND: Identification of the site of successful radiofrequency catheter ablation (RFCA) for Wolff-Parkinson-White (WPW) syndrome may be subjective. OBJECTIVE: The purpose of this study was to develop an automated signal analysis program to predict a successful ablation site. METHODS: Patients who underwent successful RFCA for WPW from 2008- 2010 at our center were analyzed. Inclusion criteria were age <21 years, loss of preexcitation in <5 seconds, and sustained success at 3 months. Exclusion criteria were congenital heart disease and pacing during RFCA. The standard recording system signal was filtered into low frequency (LF 0-≤0.02 Hz) and high frequency (HF >0.02-≤0.45 Hz). Software identified the beginning of the HF signal, LF and R-wave peaks, LF/HF signal amplitude, and area under the HF/LF signals. Successful and unsuccessful (radiofrequency energy applied without accessory pathway block) signals were compared. RESULTS: Thirty patients were analyzed; 16 had both successful and unsuccessful signals, and 14 had a successful ablation with 1 radiofrequency application. Mean age was 13.7 ± 3.1 years, weight 54.9 ± 22.4 kg, and time to accessory pathway ablation 1.7 ± 1.4 seconds. Significant differences were found between successful and unsuccessful signals in area under HF signal, LF amplitude, LF to R time, HF ratio, and HF area × HF ratio. A receiver operating curve of HF area × HF ratio produced an area under the curve of 0.89. An HF area × HF ratio of 3.1 distinguished successful from unsuccessful signals with 100% specificity and 81% sensitivity. CONCLUSION: Automated signal analysis retrospectively differentiated successful from unsuccessful signals in patients undergoing RFCA for WPW. This software may improve the safety and efficacy of RFCA in children.

The acute effects of acupuncture upon autonomic balance in healthy subjects.

Restoration of the sympathovagal (S/V) balance, involving a lowering of sympathetic and/or an augmentation of vagal modulation or a combination of both is associated with improvements in cardiovascular morbidity and mortality. To determine whether acupuncture exerts a favorable influence upon resting blood pressure and sympathovagal balance, a single-blind cross-over investigation was used to study the acute effects of acupuncture on S/V balance in normal healthy subjects. The ANOVA revealed a significant lowering of the sympathovagal balance (LF:HF) during rest for the acupuncture treatment from pre (4 +/- 2 nu) to post (2.2 +/- 1.8 nu)(p < 0.05). No such change was seen during sham treatment. The ANOVA revealed significant differences in systolic blood pressures during rest (114 +/- 4 vs. 108 +/- 3 mmHg) for the acupuncture treatment (p < 0.05). No significance was found during the sham treatment. The ANOVA failed to reveal any significant improvements in sympathovagal balance during the sustained isometric contraction. The clinical significance of these findings appears to suggest that acupuncture treatment might be beneficial in lowering blood pressure at rest. Furthermore, the lowering of the blood pressure might be in part due to a lowering of the sympathovagal balance. These findings are of importance since acupuncture treatments are non-pharmacological and have no known detrimental side-effects. This investigation employed healthy volunteers, yet acupuncture has been found to have more potent effects in animal models of hypertension and or in the presence of an autonomic imbalance.

The effect of chemoreceptor stimulation upon muscle sympathetic nerve activity.

The aim of this investigation was to quantify the combined peripheral and central chemoreceptor contribution to sympathetic outflow above (post) and below (pre) the chemoreceptor ventilatory threshold (CVT). We measured muscle sympathetic nerve activity (MSNA) in seven subjects during hypoxic/hypercapnic and room air rebreathe protocols. Comparisons were made using a repeated measures analysis of variance with two within subject factors. One factor contained three levels--hyperventilation, pre-CVT, and post-CVT. The other factor contained two levels--rebreathe and control. Total MSNA increased from hyperventilation to pre-CVT to post-CVT in the rebreathe trial (385.7+/-95.9, 592.4+/-155.7, 882.0+/-235.4 au/15s respectively) and remained constant in the control trial (433.0+/-189.3, 409.1+/-183.4, 406.1+/-161.4 au/15s respectively). Ventilation increased in the rebreathe trial only. Heart rate and blood pressure did not change in either trial. These data suggest that the chemoreceptors significantly contribute to the modulation of sympathetic outflow.